Carbon Cycle

• It is one of the most important cycles of the earth and allows for carbon to be recycled and reused throughout the biosphere (area on Earth that contains life) and all of its organisms.

In the Atmosphere

• Carbon exists in the Earth's atmosphere primarily as the gas (carbon dioxide CO₂).
• Although it is a small percentage of the atmosphere, it plays a vital role in supporting life.
• Other gases containing carbon in the atmosphere are methane and chlorofluorocarbons (CFC's).

Carbon is released into the atmosphere in several ways:

1. Through the process of respiration performed by plants and animals.

3. Combustion - Burning fossil fuels such as coal, petroleum products, and natural gas releases carbon that has been stored in the geosphere (Earth's crust) for millions of years.

Nitrogen Cycle

• Nitrogen (N) is an essential building block of amino and nucleic acids, essential to life on Earth.
• The majority of Earth's atmosphere (approximately 78%) is nitrogen.
• However, atmospheric nitrogen cannot be used by many living things.

Nitrogen Fixation

• Atmospheric nitrogen must be processed, or "fixed,"  to be used by plants and higher animals.
• Precipitation often contains substantial quantities of ammonia and nitrate, thought to result from nitrogen fixation by lightning and other atmospheric electric phenomena.

Some bacteria are able to fix nitrogen as organic nitrogen, a form that plants can use.

Shown - Cyanobacteria

Plants take nitrogen from the soil by absorption through their roots.

Decomposition releases nitrogen back into the soil or the atmosphere.